The present invention relates to an imprinter with a movable carriage having a platen roller, and, more particularly, to a lifting system for lowering the platen roller during the imprinting stroke and raising the platen roller during the return stroke.
In the past, it has been conventional practice to provide an imprinter having a platen roller which forms print impressions on one or more sheets by rolling the platen over the sheets with some pressure to engage the face of a printing plate such as a plastic credit card. During the return stroke, it is desirable to lift the platen slightly so that the imprinting operation will not take place during the return stroke. To achieve this, however, it has been necessary to provide a mechanism in the carriage itself in association with the platen assembly to form a lifting system. However, such a mechanism unduly complicates the carriage assembly and makes the cost of the imprinter that much more expensive. Furthermore, the possibility of raising and lowering a multiplicity of platen rollers becomes complicated and expensive when the lifting and lowering action is associated directly with the platen rollers.
It is an object of the present invention to overcome these problems by providing a relatively simple lifting system or mechanism which acts to lift or lower the entire carriage assembly.
It is a further object of the present invention to provide a lifting mechanism which is relatively simple in construction and therefore is relatively trouble-free.
It is a still further object of the present invention to provide a lifting mechanism which is simple in construction and which is relatively easy to construct so that the manufacturing costs for such an imprinter are reduced.
The foregoing has been achieved in accordance with the present invention by providing a platen lifting system which includes a lift cam lever and lifting cam associated with the front wheel whereby the lifting cam lever is kept under constant bias by a spring connected with an axle on the rear wheel. The lifting cam lever is adapted to engage in slots arranged along a track on the imprinter bed. The front shaft is eccentrically mounted in the lifting cam so that when the carriage is moved through the imprinting stroke the platen roller applies pressure in the area of the bed plate and as it is ready to be returned the lifting cam lever will be in registration with a slot on the track and be biased into the slot by the spring connected between the rear wheel axle and the lifting cam lever. As a result, upon return of the carriage the lifting cam lever will lift the entire carriage including the platen roller at least about sixty thousandths of an inch due to the eccentrically mounted front axle.